It is widely known that electric wires and cables utilize conductors for the transmission of signals. Typically, the cross-sectional area of conductors used in a wire or cable is chosen in view of the expected magnitude of transmission current. In a conventional audio and video signal cable, the cross-sectional area is based on three main considerations. The first is the amount of transmission current, the second is the tensile strength needed, and the third is the outer diameter required. After the conductor cross-sectional areas are calculated, other factors are considered to select the differing diameters of the conductors.
The diameter of the conductors is also typically chosen to minimize the phenomenon known as skin effect, which is present when electrical current is transmitted through wire. Briefly, when current flows through a conductor, a magnetic field is generated around the circumference of the wire. As frequency increases, the magnetic field shifts more of the electrons towards the surface of the conductor such that an electron “vacuum” results inside the middle of the conductor; no electrons pass through the center of the conductor.
Therefore, smaller diameter conductors are typically utilized for high frequency signal transmission because there is very little or no space for electron passage in lesser diameter conductors. Several approaches have been previously utilized in the art to provide a signal cable with improved transmission efficiency.
U.S. Pat. No. 4,628,151 to Cardas for a multi-strand conductor cable recognizes that the use of a variety of different sized electrical conductors, each individually insulated from one another within a cable wherein the sizes of the various conductors vary one to another according to a predetermined ratio. A common input is provided to each conductive strand at one end of the cable and a similar single connection to each of the conductive strands at the output end of the cable. Cardas teaches that the employment of different sized individual conductive strands within the cable according to the predetermined golden section ratio produces significantly improved efficiency in the transmission of signals from one end of the cable to another.
U.S. Pat. No. 6,495,763 to Eichmann, entitled “Specific Cable Ration for High Fidelity Audio Cables,” describes an audio cable where the mass in the return conductor is increased in relation to the mass of the signal conductor by a specific ratio. Basically, Eichmann teaches that the use of a specific ratio of diameters and cross-sectional areas between the signal and the return provides a faster pathway for electrons to travel.
In conventionally used electric wire, the center conductor is typically a single conductor, and if the conductor is too narrow, electrical resistance increases. However, if the conductor is too large, then high frequency signal passage is difficult.
The problem with the cables known in the art is that these cables utilize conductor shapes and materials that are not designed to effectively carry more than one type of signal frequency. For example, although it is known that signal carrying cables can comprise conductor strands other than round, i.e., square, flat, rectangular, etc., in a typical currently known cable, all of the conductors have the same shape.
When such cables are used to simultaneously transmit at different bands of frequency (i.e., high, medium, and low frequencies), the problem of phase difference occurs, and also there may be differences in amplitude throughout the audio frequency range. Due to skin effect issues, and differences in wire gauges, different frequency ranges may be reproduced with varying degrees of accuracy and amplitude, and some interference may take place between different frequency ranges causing loss of definition.
Accordingly, there is a need for a for a multi-core audio/video signal cable that is capable of providing a balanced high, medium and low frequency response, as well as better definition.